There are several commercial and industrial buildings which now surpass 60 stories or more. These buildings all need tall cranes to be able to help transport the materials to the higher floors. There are cranes which are operated from the back of trucks or other types which have their own vehicle attached. Tower cranes are the biggest kinds on the market.
Tower cranes are the stand-alone structures that are normally found on high-rise building projects. Usually, they are part of a major city's downtown skyline. When new construction like for instance skyscrapers or apartment buildings and commercial facilities such as shopping center are being constructed, chances are a crane will be on site.
Kinds
There are two different types of cranes: jib crane of the boom crane. The jib is a metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts things. On a luffing kind of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both kinds can vary from 30 pounds to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast which is composed of separate [parts. The parts are added to increase the overall height of the machinery. The mast extends upward to wherever the desired height is, to the control module, which is a small room which has glass windows on all four sides or to the tower as it is also called. The crane operator works from inside of the tower.
Lift
The crane utilizes a braided metal cord to be able to raise supplies. This cord extends out from a motor located near the control module to the end of the boom or jib. There is a pulley system situated at the end of the jib, through which the cord is positioned and lowered down. The jib that holds the cord becomes balanced by a counter jib located on the tower's opposite side. The counter jib has weights. These weights help to prevent the crane from toppling over when heavy materials are lifted.